Weeks of disturbances prompted the Bahraini ruler to impose martial law and invite foreign troops to help to restore order.

Scores of doctors are reported to have been detained by security forces apparently for treating injured protesters. Another guest, King Mswati III of Swaziland, has been criticised by Amnesty International after using armed security forces to crush peaceful demonstrations.

Mr Tatchell said: “It’s deplorable that the Queen has invited royal dictators from Bahrain, Swaziland and Saudi Arabia who preside over severe human rights abuses, including detention without trial, torture and violent repression of protests.”